Horizontal Wave Pressures on the Crown Wall of Rubble Mound Breakwater under Non-Breaking Condition

The crown wall with parapet on top of the rubble mound breakwater represents a relatively economic and efficient solution to reduce the wave overtopping discharge. However, the inclusion of parapet leads to increased wave pressure on the crown wall. The wave pressure on the crown wall is investigated by physical model test. To design the crown wall the wave loads should be available, and the horizontal wave pressure is still unclear. Regarding to the horizontal wave pressure on the crown wall, a series of experiments were conducted by changing the rubble mound type structure and the wave conditions. Based on these results, pressure modification factors of Goda’s (1974, 2010) formula have been suggested, which can be applicable for the practical design of the crown wall of the rubble-mound breakwater covered by tetrapods.

Applicability of the Numerical Simulation of the Impulsive Wave Pressure of Solitary Waves

To evaluate the destruction of structures by tsunami forces, it is desirable to correctly evaluate not only the sustained forces due to the water level but also the impact forces generated at the tsunami front. To this end, it is necessary to conduct numerical simulations based on the three-dimensional Navier–Stokes equations, but the validity of the calculation results is not guaranteed. Therefore, this study compares the results obtained blind before confirming the experimental results and the results obtained by adjusting the parameters after confirming the experimental results. Recommendations are made to resolve issues that arise.

Blind-Test Numerical Simulation of Tsunami Wave Pressure Acting on a Land Structure

The prediction performance of numerical models of tsunami wave pressure on land structures was investigated using blind tests. Two types of numerical models were used, based on the volume-of-fluid (VOF) method. Both models reproduced the experimental results well for water-level time series. For wave-pressure time series, some differences were observed between the two models in the vertical distribution of wave pressure during the initial rise. In both models, however, the experimental results showed that overall trends for total wave force were in good agreement. The experimental results produced a value slightly higher than the maximum wave force, suggesting that caution is needed when designing structures to ensure that wave force is not underestimated.

Dependency of the Blast Wave Pressure on the Amount of Used Booster

Most of the damage caused by an explosion is caused by a pressure effect. The magnitude of the pressure generated by the explosion is influenced by the external characteristics of the environment (surrounding objects, their arrangement, geometry, etc.) and internal characteristics (type of explosive, type of charge, booster and others). An effective combination of internal factors creates a symmetry that results in the highest possible value of pressure generated by the charge explosion. The paper focuses on the influence of the booster reaction on this symmetry. The scope of the paper is to understand the dependency of the blast wave pressure on the amount of used blaster to increase the efficacy of explosions on the environment and structures to increase the protection of affected structures. The open-air field tests were conducted using different types of explosives: trinitrotoluene and three different types of industrially made ANFO explosives (pure ammonium nitrate and fuel oil, ammonium nitrate and fuel oil plus aluminum powder, ammonium nitrate and fuel oil mixed with trinitrotoluene). The obtained data were compared with the analytical approach for setting the generated maximal pressure on the front of the blast wave.

Numerical Study on Propagation of Ice Breaking Shock Waves in Process of Breaking Ice by Double-Layer Charge Blasting

The ice-breaking process of the double-layer charge at a depth of 150 cm underwater is simulated by LS-DYNA. This paper analyzes the load type, shock wave pressure characteristics and propagation behavior of the double-layer charge during underwater explosion. By analyzing the impact of the shock wave pressure in the water under different charge intervals and time intervals on the shock wave pressure of the double charge, it is concluded that the peak pressure of the double charge explosion shock wave is jointly determined by the double charge. In this range, the second peak pressure value of the drug is greater than the pressure value of the first peak of the drug, and the attenuation is slow; the delay time of the upper charge has little effect on the peak pressure value of the shock wave in the water; the delay time is higher than that of the lower charge Initiation, at the same position, the total pressure peak of the shock wave formed by the delay of the upper charge is larger.

Automatic Tsunami Barrier

The Anti-Tsunami Laboratory (ATL) invented and developed the Anti-Tsunami Door (ATD) barrier as an automatic tsunami barrier. In September 2018, ATL and Kyoto University tested a mid-scale model of a three-stage ATD unit and confirmed its performance: (1) functioning automatically (refer to Figure 9); (2) achieving reasonable wave height reduction, which is approximately 40%–80% that of a solid barrier of the same height; and (3) demonstrating reasonable strength for a wooden structure under the mid-scale model test conditions. ATL had planned to test a large-scale model of an ATD unit in Oregon State University in May 2020, but that test has been delayed owing to the COVID-19 pandemic. Because the wave pressure on the ATD unit is expected to be high during the large-scale model test, ATL requested that the Explosion Research Institute (ERI) simulate the wave pressure on a large-scale model ATD unit, and based on the results, ATL will reinforce the ATD unit. After testing the large-scale model unit, ATL will install ATD barriers along the coast of Japan, customizing the barrier for specific tsunami hazards.